Prevalence and Severity of Iron Overload
All subjects had an abdominal MRI (n=102, 99%) to assess LIC except one who had a cardiac MRI only. MRI iron evaluation was completed at a mean of 3.2 years ( 2 months to 12.5 yrs) after initial cancer diagnosis, which was after end of therapy in 73 of 103 subjects (71%) at a mean 1.9 (range 0.01 to 9.1) years. Of the 30 subjects who had IO evaluation prior to end of therapy, 17 (57%) were assessed in anticipation of HSCT, while the remaining 13 subjects were assessed due to various clinical concerns. Figure 1 demonstrates the distribution of subjects by severity of siderosis in each organ assessed. Of the 102 subjects with LIC evaluated, 53% had moderate or greater IO (LIC ≥7 mg/g dry liver weight [DLW]). Of the 96 subjects with pancreatic iron quantification, 80% (77/96) had evidence of pancreatic siderosis (pancreatic R2* >27), and 16% (15/96) had severe siderosis (R2* >100). Borderline cardiac siderosis (T2* <30) was found in 12.5% (10/80) of subjects and true cardiac siderosis (T2* <20) in 4% (3/80). Of the 29 patients assessed for pituitary involvement, 6 patients had pituitary siderosis, 5 had pituitary volume loss and 2 patients had both.
Hepatic siderosis was associated with pancreatic siderosis (p <0.0001) but not cardiac or pituitary siderosis, while pancreatic iron was predictive of both cardiac (p=0.0043) and pituitary iron (p=0.0101). All patients that had evidence of pituitary siderosis had evidence of pancreatic iron deposition as well, and only patients with severe pancreatic iron overload (>100Hz) were noted to have moderate or greater cardiac siderosis. Neither hepatic nor pancreatic siderosis in patients with stem cell transplant differed from non-transplanted subjects (p=0.4378, p=0.7275, respectively), even when limited to allogeneic transplant (p=0.6435, p=0.3798). There was no association between IO and cancer type. Among subjects treated for leukemia/lymphoma, higher LIC was observed in subjects treated for AML or high-risk ALL compared to other cancer types (median LIC 8.5 vs. 2.9 mg/g DLW, p=0.0011), regardless of whether they had received HSCT. Based on the Treatment Rating Scale (ITR-3), the majority of subjects (70/103) received the most intensive treatments, while 30 subjects received very intensive and two subjects received moderately intensive treatments. There was no association between the ITR-3 score and IO (p=0.1870).